<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>demo 2-3</title>
	</head>
	<body>
	</body>
	<script>
		var a=1000;
		function f(){
			console.log(a);
			if(false){
				var a = "ni hao";
			}
		}
		f();
	</script>
</html>